Abstract
Tectonic coal has become an important research topic for preventing coal mine disasters and for exploring and developing coal-bed methane resources. To investigate the mechanical and acoustic properties of tectonic coal, we conducted a uniaxial compression test for tectonic and non-tectonic coal, and acoustic emission (AE) signals have been simultaneous captured in the compression process. The AE energy and waiting time of events have been studied statistically. The results show that the probability density function of AE energy follows the power law distribution well, and indicates that the AE of non-tectonic coal is mainly generated from the fracture source, while the probability density function distribution of tectonic coal is the mixing result of fracture and friction effects. Only the waiting time distribution of non-tectonic coal follows the typical brittle fracture’s double power law behavior. The waiting time distribution of tectonic coal shows the single power law with a smaller exponent value, which is associated with the granular microstructure of tectonic coal. The distribution of aftershock and Båth’s law are not sensitive to microstructure, and are identical for non-tectonic and tectonic coal. At last, the correlation dimension results for the spatial distribution of AE hypocenters indicated that the rough continuous decrease in multifractal dimension might be a precursor to devastating destruction.
Highlights
Tectonic coal, formed after the intact coal being subjected to long-term intense squeezing, shearing and deformation, is characterized by low strength, a high gas content, fast desorption, and low permeability [1]
The low strength characteristics of tectonic coal reduce the mechanical conditions for outburst, and the tectonic coal is easy to form a large quantity of small coal particles, which have a fast gas desorption rate
The main purpose of this study is first to show if tectonic coal and non-tectonic coal have different acoustic characteristics under compression, and whether the statistical physical analysis is sensitive to the collapse of tectonic coal, and can be used as potential disaster forecast technology
Summary
Tectonic coal, formed after the intact coal being subjected to long-term intense squeezing, shearing and deformation, is characterized by low strength, a high gas content, fast desorption, and low permeability [1]. The low strength characteristics of tectonic coal reduce the mechanical conditions for outburst, and the tectonic coal is easy to form a large quantity of small coal particles, which have a fast gas desorption rate. Tectonic coal has a close relationship with the preparation and occurrence of coal and gas outburst disasters [2]. Tectonic coal is an important research object for coal mine disaster prevention and for the exploration and use of coal-bed methane resources [5,6,7,8]. Relative to non-tectonic coal, tectonic coal has low compression strength, low permeability, and a high absorption and desorption capacity. In the process of tectonic coal generation, considerable amounts of methane are produced when the stacked aromatic rings are shed as hydrocarbon chains
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